Alexander finished his junior campaign with 103 tackles, seven tackles-for-loss and 1.5 sacks. In his final game, Alexander led Oklahoma with 12 tackles against No. 1 Clemson in the College Football Playoff semifinals.

Since seeing playing time as a true freshman in 2013, Alexander has played in 39 games and started 34 contests. The two-year starter's sudden departure forces assistant Tim Kish to develop and replace one of its two inside linebacker positions, which should return junior Jordan Evans next season.

The Big 12 announced Alexander as a first-team All-Big 12 linebacker for the time in his collegiate career. He was a second-team All-Big 12 selection by the AP in 2014 and the 2013 Big 12 Defensive Freshman of the Year by the coaches.

The 6-foot linebacker was a consensus three-star recruit out of Tulsa Booker T. Washington High School. He will now try his hand at the NFL after a productive three seasons with Oklahoma and leave the door open for redshirt freshman Tay Evans, Alexander's 2015 back-up, to step in to a starting role next season. True freshmen Ricky DeBerry, Arthur McGinnis and sophomore Ogbonnia Okoronkwo will also vie for playing time at linebacker.